Conditional styles and free-association thereon

["Bart Schaefer" <schaefer@xxxxxxxxxxxxxxxxxxxxxxx>]

On May 12,  9:27am, Sven Wischnowsky wrote:
} Subject: Re: PATCH: Re: "Cancel" menu selection & Co?
}
} Aside: I've been playing with a little completer named `_guard' that
} works a bit like _prefix and _ignored, i.e. it looks up completers
} and calls them -- based on some condition.  [...]
} 
} I then decided that I don't like this approach. Then I thought again
} about adding conditionals to styles. For testing purposes, this could
} be implemented by a new completion widget that calls _main_complete,
} but defines a `zstyle' function before that.  [...]  Using shell syntax
} here could mean that the wrapper makes every style value be eval'ed as 
} a whole [...]

The basic concept here isn't bad, but I'm not excited by the potential
implementation.  It's a bit like implementing "while" as a function that
takes the loop condition and loop body in arguments.  (Which I have done,
long ago and far away in another scripting language, and not been very
happy about.)  You can make it work, but it's going to feel wrong every
time you use it, even if you don't have to struggle with the quoting.

We're reaching the point -- if _arguments hasn't passed it already --
where we need help from the lexer to proceed sanely.  Writing this kind
of thing in Tcl, for example, would be much cleaner, because { ... }
is -always- parsed approximately the way zsh parses a function body.
(Not that Tcl doesn't have plenty of other warts/problems of its own.)

On a slightly different note ... every time "eval"ing something else
gets mentioned, I worry again that the completion system has created a
security hole you culd drop all of Microsoft through.  The number of
things that autoload and execute when you press TAB has exceeded all my
expectations from when I first began discussing a function-based system.
I'm on the verge of suggesting that the zsh/complete module should refuse
to load if EUID == 0.

At the least, shouldn't compinit check the directories (and files?) in
$fpath for unsafe write permissions?

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com